Fusing apparatus

ABSTRACT

Fusing apparatus for fusing a toner image in which a flash lamp is supported in a cooling tube and cooling air is circulated through the tube around the lamp. The cooling tube includes an aperture by which air can be introduced into the fuser housing to maintain the housing at a positive pressure. The housing is formed of an inner and outer shell which define an insulating air gap therebetween.

United States Patent 1191 Lux Oct. 16, 1973 [5 FUSING APPARATUS 2,783,697 3/1957 Eisner et al 263/6 3,700,218 10/1972 Laisney 263/6 [75] Inventor- Penfield, 3,626,424 12/1971 Kahn 240/47 [73] Assignee: Xerox Corporation, Stamford, 313991613 9/1968 M 240/47 Conn 3,598,486 8/1971 Kushima 355/67 3,492,458 1/1970 White et a]. 219/216 [22] Filed: May 5, 1972 Prima Examiner-John J. Camb 21 A LN .1250635 Y 1 pp 0 Assistant Examiner-Henry C. Yuen Att0rney.lames J. Ralabate et a1. [52] US. Cl. 432/233, 240/47, 219/216,

355/3, 355/67, 432/227, 432/59 57 ABSTRACT [51] Int. Cl. F2lv 29/00, F27b 15/16 58 Field of Search 263/6 E, 8; 219/8, Fusmg apparatus fusmg a toner Image m whlch a v 219L216 355/3, 11, 12 67; flash lamp is supported in a cooling tube and cooling 4 227 air is circulated through the tube around the i The cooling tube includes an aperture by which air [56] References Cited can be introduced into the fuser housing to maintain the housing at a positive pressure. The housing is UNITED STATES PATENTS formed of an inner and outer shell which define an in- SDtreich 240/47 Sulating air gap therebetween' 1 avls .1 3,566,076 2/ 1971 Frantuzzo 263/6 12 Claims, 5 Drawing Figures PATENIEDnm 16 ms SHEET 20F 2 M. mwm mg m m9 0 mm- FUSING APPARATUS.

- BACKGROUND OF THE INVENTION This invention relates to electrostatography, and more particularly to an improvement in the fusing station of an electrostatographic recording apparatus.

Electrostatography is exemplified by the basic electrophotographic process taught by C.F. Carlson in U.S. Pat. No. 2,297,691, which involves placing a uniform electrostatic charge on a photoconductive insulating layer, exposing the layer to a light and a shadow image to dissipate the charge on the areas of the layer exposed to the light and developing the resulting latent electrostatic image by depositing on the image a finely-divided electroscopic material referred to in the art as toner. The toner is normally attracted to those areas of the layer which retain a charge, thereby forming a toner image corresponding to the latent electrostatic image,

which may then be transferred to a support surface,

such as paper.

In general, the powder image is affixed to a transfer sheet by a heat fusing technique and among such techniques there may be mentioned oven fusing, hot air fusing, radiant fusing, flash fusing and the like. Flash fusing is a highly desireable fusing technique in that such a technique is efficient for both normal and high speed copying. Flash fusing is generally effected by the use of a gas lamp, such as a Xenon lamp, from which radiant energy is directed onto the surface ofa recording sheet, containing a powder image, conveyed past the lamp. The radiant energy is reflected by those areas of the recording sheet which do not bear toner, while the toner on the other areas of the recording sheet absorb the radiant energy in the form of heat which is sufficient to effect the desired fusing.

The flash fusing technique evolves a high quantity of heat which must be effectively dissipated. In addition, the flash fusing assembly must be capable of being easily serviced. Furthermore, the flash fusing assembly should be designed to provide for a clean operation thereof; i.e., minimize or eliminate the entrance of foreign material, in that the presence of contaminants on the interior surfaces of the housing reduces the reflecting ability thereof.

SUMMARY OF THE INVENTION improved fusing apparatus.

Another object of the present invention is to provide an improved flash fusing apparatus.

A further object of the present invention is to provide a flash fusing apparatus in which heat is effectively dissipated.

Still another object of the present invention is to provide a flash fusing apparatus in which the apparatus is kept free of foreign material.

These and other objects of the present invention should be more apparent from reading the following description of the invention.

The objects of the present invention are accomplished in one aspect by providing a fusing apparatus for fusing a powder image onto a transfer or recording sheet in which the heating means for effecting the fusing is supported in a cooling tube which is connected to a cooling circuit for circulating a coolant through the cooling tube.

More particularly, the fusing apparatus includes a housing having an inlet and outlet for introducing and withdrawing a transfer sheet bearing a powder image. A flash lamp is supported in a cooling tube positioned in the housing transverse to the path of the transfer sheet and a coolant, preferably atmospheric air, is circulated through the cooling tube and around the flash lamp to prevent overheating.

In accordance with another aspect of the present invention, a portion of the cooling tube within the housing is provided with at least one aperture whereby air circulating through the cooling tube circulates through the housing thereby maintaining the housing at a positive pressure. The positive pressure functions to maintain the housing free of extraneous contaminants.

In accordance with a further aspect of the present invention, the housing is a double walled housing having an air gap therebetween which functions to insulate the housing.

The invention will be described in more detail with respect to a preferred embodiment thereof illustrated in the accompanying drawings but it is to be understood that the scope of the invention is not limited to such a preferred embodiment.-

THE DRAWINGS FIG. 1 is a simplified schematic representation of electrophotographic apparatus including the fusing apparatus of the present invention;

FIG. 2 is a side elevation of the fusing apparatus of the present invention;

FIG. 3 is a rear elevational view of the fusing apparatus of FIG. 2;

FIG. 4 is a front and side elevational view of a support for the fusing lamp of the fusing apparatus of FIG. 2; and

FIG. 5 is a front and side elevational view of an electrical connection for the fusing lamp of the fusing apparatus of FIG. 2. 7

Referring now to the drawings, there is shown schematically in FIG. 1 an embodiment of the subject invention in a suitable environment such as an electrophotgraphic reproducing machine adapted for continuous and automatic operation. The machine includes an electrophotographic plate or surface 10 formed in the shape of a drum. The plate has a photoconductive or light responsive layer on a conductive backing, journaled in a frame to rotate in the direction indicated by the arrow. The rotation will cause the plate to sequentially pass a series of electrophotographic processing stations. For the purpose of the present disclosure, the several electrophotographic processing stations in the path of movement of the plate surface may be described functionally as follows:

A charging station A at which a uniform electrostatic charge is deposited on the photoconductive plate;

An exposure station B at which a light or radiation pattern of the copy to be reproduced is projected onto the plate surface to dissipate the charge in the exposed areas thereof to thereby form a latent electrostatic image of the copy to be reproduced;

' A developing station C at which electrostatographic developing material, including toner particles having an electrostatic charge opposite that of the latent electrostatic image is cascaded over the plate surface whereby the toner particles adhere to the latent electrostatic image to form a visible toner image in a configuration of the copy being reproduced;

A transfer station D at which the toner image is electrostatically transferred from the plate surface to a transfer material or a support surface and A drum-cleaning station E at which the plate surface is brushed to remove residual toner particles remaining thereon after image transfer and exposed to a relatively bright light source to effect substantially complete discharge of any residual electrostatic charge remaining thereon.

It is felt that the preceding description of the electrophotographic process is sufficient for an understanding of the instant invention. Further details of this type of electrophotographic apparatus may be had by reference to U.S. Pat. No. 3,30l ,126 issued to RF. Osborne et al.

In addition to the apparatus disclosed in aforementioned Osborne et al patent, the electrophotographic machine is also provided with fixing apparatus to permanently bond thetoner image to the backing sheet and which forms the basis of the instant invention.

The sheet material, preferably paper, which is to form the final support for the permanent toner image, as shown, is a web of material 12 wound about a support roll 14 at a supply station. The web is directed along a feed path to pass the transfer station D and guided by an idler roll 22 through a light attenuator 20 described in detail in copending U.S. application Ser. No. 250,636 filed concurrently herewith and into the fuser assembly 100 of the present invention. The web having the fused image thereon is guided from the fuser assembly by a roller for ultimate withdrawal from the machine. The web may be subsequently cut into sheets as known in the art.

The fuser assembly l includes a fuser housing 101 comprised of an upper section 102, defining a top wall 103, side walls 104 and 105,front wall 106 and a rear wall 107, and a lower section 108, defining a bottom wall 109. The bottom of the front and rear walls 106 and 107 of the upper section 102 are provided with outwardly extending longitudinal flanges Ill and the bottom section 108 is provided with longitudinal spacing bars 112 which extend parallel to the flanges 111 and are afflxed thereto by suitable fastening means, such as screws 113. In this manner, the bottom wall 109 is spaced from each of the side walls 104 and 105 to define therebetween transfer sheet inlet and outlet slits 114 and 115, respectively, for introducing and withdrawing a transfer sheet into and out of the fuser housing'l01. The side wall 105 is further provided with a resilient seal means 1 16 which extends over the outlet slit 1 and is in contact with the bottom wall 109, with the transfer sheet being withdrawn from the housing 101 between the seal means 116 and the bottom wall 109. The seal means 116 is provided to inhibit leakage of light from the fuser.

The interior of the upper section of the fuser housing 101 is provided with an inner liner or shell 117 integrally connected to the upper section 102 and spaced therefrom to provide an insulating air gap 118 therebetween. The inner surface 119 of the shell 117 is provided with a light reflecting surface to maximize the transfer of heat to the transfer sheet being passed through the fuser housing 101.

The fuser heating assembly 121 is comprised of a .high intensity radiation source such as a pair of spaced flash lamps 122 each centrally positioned in cylindrical glass cooling tubes 123 which are positioned transverse to the path of a transfer sheet through the fuser housing and which extend through aligned apertures 124 in the front and rear walls of the housing 101. An insulating tube 125, formed of a suitable insulating material, is telescopically received over the ends of each of the cooling tubes 123 and includes a collar receiving exterior radial flange 126 and an O-ring receiving interior circular shoulder 127. A fastening collar 128 is received over the flange 126 of insulating tube and is removably fastened to the housing 101 by suitable fastening means, such as screws 129. An O-ring- 131 is positioned on the shoulder 127 of insulating tube 125, and is seated into sealing contact with the shoulder 127, housing 101 and cooling tube 123 by tightening of the screws 129 on collar 128.

The flash lamps 122 are centrally supported in the cooling tubes 123 by retaining means in the form of resilient clips 141 which are removably received on the metal terminals 142 of the flash lamps 122, which extend exteriorly of the cooling tubes 123. The clips 141 are comprised of a single resilient wire formed into a convoluted central portion 143 defining a cylindrical opening 144, axially spaced oppositely curved arcuate outer portionsl45 and 146, which function as supporting legs, connected to the axially spaced ends of the central portion 143 by curved intermediate portions 147 and 148. The arcuate outer portions 147 and 148 are preferably each curved about equal radii having their respective centers along the central axis of the cylindrical opening 144 with each of the radii being such that the flash lamps 122 are positioned at about the center of the cooling tube 123.

The flash lamps 122 are mounted in the retaining clips 141 by spreading the top of the outer portions 145 and 146 to enlarge the opening 144 and placing the terminals 142 into the enlarged opening 144. Releasing'of the outer portions 145 and 146 of the clip 141 results in the central portion 143 gripping the terminals 142 of the flash lamp 122.

Electrical connectors generally indicated as 151, are mounted on the terminals 142 of the flash lamps 122 adjacent to the retaining clips 141. The electrical connector 151 are comprised of axially spaced parallel vertical arms 152 and 153 connected to each other by a horizontal connecting base 154 whereby the connectors 151 have a generally U-shape. The arms 152 and 153 are provided with axially spaced aligned apertures 155 and 156 which are slidingly fit over the lamp terminals 142. The upper ends of the arms 152 and .153 are provided with aligned screw holes adapted to receive a screw 157. The tightening of screw 157 causes the ends of arms 152 and 153 to move axially toward each other, thereby changing the effective diameter of the apertures 155 and 156, and providing a gripping connection between the connector 151 and the metal terminal 142. An electrical wire 158 which enters the interior of the insulating tube 125 through an aperture including a suitable seal, such as O-ring 161, is removably fastened to the base 154 of connector 151 by a suitable fastening means, such as a screw 162. in this manner, the lamp terminals 142 are facilely connected to a suitable circuit and the electrical connection may be readily removed by the use of a screw driver which can easily be inserted into the insulating tubes 125.

The flash lamps 122 may be of a type known in the art, such as a quartz tube filled with a suitable gas, such as Xenon gas. The flash lamp 122 includes axially spaced electrodes 171 and a trigger coil 172 wrapped around the exterior of the gas filled tube. The trigger coil 172 is connected to a trigger circuit, of a type known in the art, which when activated provides a suitable high voltage pulse to the trigger coil 172. The operation of the flash lamp is well-known in the art and no detailed explanation thereof is deemed necessary for a full understanding of the present invention. Further details with respect to flash fusing lamps may be obtained by reference to U.S. Pat. No. 3,465,203; U.S. Pat. No. 3,445,626; and U.S. Pat. No. 3,529,129.

The flash lamps 122 are cooled by a coolant, preferably air obtained from the atmosphere, circulated through a cooling circuit which includes cooling tubes 123 and a pair of parallel transverse tubular return ducts 181 affixed to the outer portion of the lower section 108. The insulating tubes 125 positioned on the rear wall 107 of housing 101 are connected through suitable duct work in fluid flow communication with a source of cooling air under pressure, such as a centrifugal blower which obtains cooling air from the atmosphere, and the insulating tubes 125 positioned on the front wall 106 of housing 101 are in fluid flow communication with the return ducts 181 through removable right angle connectors 182 and 183. The return ducts 181 are in fluid flow communication with suitable ducts for withdrawing the cooling air from the machine. In this manner, cooling air obtained from the atmosphere may be circulated around the flash lamps 122 and subsequently returned to the atmosphere.

In accordance with a particularly preferred embodiment of the present invention, each of the cooling tubes 123 at the portion thereof within the housing 101 adjacent to the rear wall 107 is provided with a small aperture 191 whereby air under pressure is introduced into the interior of housing 101. The small quantity of air introduced into the housing 101 circulates through the housing and is released therefrom through the recording sheet inlet and outlet slits 114 and 115. In this manner, the interior of the housing 101 is maintained under positive pressure and such positive pressure functions to maintain the interior of the housing essentially free of any machine or atmospheric dirt which could normally enter the housing 101.

In operation, a recording sheet having a toner image thereon is passed through the fuser housing, and the flash lamps are operated in a timed sequence, as known in the art, to insure fusing of the toner image thereon. Air is circulated by the centrifugal blower through the cooling tubes 123 and a small quantity thereof is introduced into the housing through the aperture in the cooling tube to maintain the housing at a positive pressure. In this manner, excess heat is effectively dissipated and the housing is maintained free of foreign contaminants which could reduce the reflectance from the interior surfaces thereof.

Numerous modification and variations of the hereinabove described embodiments are possible within the spirit and scope of the present invention. Thus, for example, the return ducts for the coolant may be separate from the flash fuser housing instead of integrated therewith as particularly described.

It is also to be understood that although the present invention has been particularly described with respect to an electrophotographic reproducing machine using a rotating drum as a recording surface, the present invention may also be employed in machines employing other types of recording surfaces; e.g., a rotating belt.

It is to be understood that the present invention is also applicable to electrostatographic processes other than the electrophotographic type, such as for example, electrostatic processes in which an electrostatic la" tent image is formed by a pulsing electrode.

The above modifications and others should be apparent to those skilled in the art from the teachings herein.

The present invention is particularly advantageous in that excess heat generated in the flash fuser apparatus is facilely and effectively dissipated while simultaneously maintaining the apparatus essentially free of foreign contaminants. In addition, the overall apparatus as a result of its overall construction is easily services.

These and other advantages should be apparent to those skilled in the art from the teachings herein.

Numerous modifications and variations of the present invention are possible in light of the above teachings and, therefore, within the scope of the appended claims the invention may be practised other than as particularly described.

What is claimed is:

l. A fusing apparatus for fusing a powder image on a recording sheet, comprising:

a housing, said housing including an inlet for introducing a recording sheet having a powdered image thereon into the interior of the housing and an outlet for withdrawing a recording sheet having a fused image thereon from the interior of the housing; a cooling tube within the housing; means sealing fastening said cooling tube to said housing; heating means for fusing the powder image on said recording sheet supported in said cooling tube; and means for circulating a coolant gas, under positive pressure, through said cooling tube whereby coolant flowing through the cooling tube flows around said heating means.

2. The apparatus of claim 1 wherein said cooling tube contains at least one aperture for providing fluid flow communication between the cooling tube and said housing interior to maintain said housing interior at a positive pressure.

3. The fusing apparatus of claim 1 wherein said heating means is a flash lamp.

4. The fusing apparatus of claim 2 wherein said hous ing is comprised of an inner and outer shell, said inner and outer shell being spaced from each other to define an insulating air gap.

5. A flash fusing apparatus for fusing a powder image on a recording sheet comprising:

a housing including a recording sheet inlet at one end thereof and recording sheet outlet at the other end thereof for passing a recording sheet having a powder image thereon into and out of said housing; at least one cooling tube positioned in said housing transverse to the path of a recording sheet from said inlet to said outlet, said cooling tube extending through oppositely aligned apertures in said housing; means for fastening said cooling tube to said housing; a flash lamp for providing heat to fuse the powder image intermediately positioned in said cooling tube; support means for supporting said flash lamp in said cooling tube; and means for circontains at least one aperture for providing fluid flow communication between the cooling tube and said housing interior to maintain said housinginterior at a positive pressure.

7. ln combination with an electrostatographic apparatus, a fusing apparatus for fusing a powder image on a recording sheet comprising:

a housing including an inlet for introducing a recording sheet having a powder image thereon and an outlet for withdrawing a recording sheet having a fused image thereon; a cooling tube positioned in the housing; means fastening the cooling tube to the housing; a high intensity radiation heating means for fusing the powder image on said recording sheet positioned in said cooling tube; and means for circulating a coolant gas, under positive pressure through said cooling tube, whereby coolant can be circulated through said cooling tube around said high intensity radiation heating means.

8. The combination of claim 7 wherein said cooling tube contains at least one aperture for providing fluid flow communication between the cooling tube and said housing interior to maintain said housing interior at a positive pressure.

9. The combination of claim 7 wherein said housing is comprised of an innerand outer shell, said inner and outer shell being spaced from each other to define an insulating air gap. U

10. The combination of claim 8 wherein said radiation heating means is a flashlamp.

11. The combination of claim 10 wherein the inlet and outlet are at opposite sides of said housing, said cooling tube and and flash lamp supported therein -tening means removably connecting said upper and lower sections with the upper and lower sections at opposite sides being spaced from each other to define said inlet and outlet. 

1. A fusing apparatus for fusing a powder image on a recording sheet, comprising: a housing, said housing including an inlet for introducing a recording sheet having a powdered image thereon into the interior of the housing and an outlet for withdrawing a recording sheet having a fused image thereon from the interior of the housing; a cooling tube within the housing; means sealing fastening said cooling tube to said housing; heating means for fusing the powder image on said recording sheet supported in said cooling tube; and means for circulating a coolant gas, under positive pressure, through said cooling tube whereby coolant flowing through the cooling tube flows around said heating means.
 2. The apparatus of claim 1 wherein said cooling tube contains at least one aperture for providing fluid flow communication between the cooling tube and said housing interior to maintain said housing interior at a positive pressure.
 3. The fusing apparatus of claim 1 wherein said heating means is a flash lamp.
 4. The fusing apparatus of claim 2 wherein said housing is comprised of an inner and outer shell, said inner and outer shell being spaced from each other to define an insulating air gap.
 5. A flash fusing apparatus for fusing a powder image on a recording sheet comprising: a housing including a recording sheet inlet at one end thereof and recording sheet outlet at the other end thereof for passing a recording sheet having a powder image thereon into and out of said housing; at least one cooling tube positioned in said housing transverse to the path of a recording sheet from said inlet to said outlet, said cooling tube extending through oppositely aligned apertures in said housing; means for fastening said cooling tube to said housing; a flash lamp for providing heat to fuse the powder image intermediately positioned in said cooling tube; support means for supporting said flash lamp in said cooling tube; and means for circulating cooling air under positive pressure through said cooling tube.
 6. The apparatus of claim 5 wherein said cooling tube contains at least one aperture for providing fluid flow communication between the cooling tube and said housing interior to maintain said housing interior at a positive pressure.
 7. In combination with an electrostatographic apparatus, a fusing apparatus for fusing a powder image on a recording sheet comprising: a housing including an inlet for introducing a recording sheet having a powder image thereon and an outlet for withdrawing a recording sheet having a fused image thereon; a cooling tube positioned in the housing; means fastening the cooling tube to the housing; a high intensity radiation heating means for fusing the powder image on said recording sheet positioned in said cooling tube; and means for circulating a coolant gas, under positive pressure through said cooling tube, whereby coolant can be circulated through said cooling tube around said high intensity radiation heating means.
 8. The combination of claim 7 wherein said cooling tube contains at least one aperture for providing fluid flow communication between the cooling tube and said housing interior to maintain said housing interior at a positive pressure.
 9. The combination of claim 7 wherein said housing is comprised of an inner and outer shell, said inner and outer shell being spaced from each other to define an insulating air gap.
 10. The combination of claim 8 wherein said radiation heating means is a flash lamp.
 11. The combination of claim 10 wherein the inlet and outlet are at opposite sides of said housing, said cooling tube and flash lamp supported therein being positioned transverse to the path of a recording sheet from said inlet to said outlet.
 12. The combination of claim 11 wherein said housing is comprised of an upper and lower section, and fastening means removably connecting said upper and lower sections with the upper and lower sections at opposite sides being spaced from each other to define said inlet and outlet. 